Mineral oil composition



Patented Aug. 9, 1949 Frederic L- Matthews, St. Louis, Mo., assi'gnors to Monsanto Chemical Company, a. corporation .of Delaware N0 Drawing. Application February 26,1946, Serial No. 650,388

4 Claims. (Cl. 252-59 This invention relates to mineral oil composie tions.

Anobject of this invention isto provide min eral oil compositionshaving an increased viscosity over ordinary mineral oils. A further object is toprovid'e alubricating; composition having a relatively fiat viscosity-temperature relationship. A still further object is to provide a; lubricating oil possessing good resistance. to shearv These and other objectsare provided by our new mineral oil composition wherein polymerizedcyclohexylstyrene in soluble'formis combined with a mineral lubricating oil.

According to our discovery; monomeric cycio-' hexyl'styrene is polymerized with or without the application of heat and with or'without polymerization catalysts being present to yield a polymer which. is solublein ordinary lubricating oils. We have found that solutions of polycyclohexylstyrene inv oils exhibit a decreased temperature. coefiicientofviscosity over mineral oils which. do not contain this material: The viscosity of such solutions has been found to be remarkably resistant to the action ofi heat. We have also found that polycyclohexylstyrene has a tendency to inhibit the crystallization of naturally occurring, waxes present in mineral oils.

Polymerization of cyclohexylstyrene to theoil soluble polymer may be carried out according to any of theusualpolymerization methods; These methods involve polymerization in mass,insoluti'onor'in aqueous emulsion or suspension.

Suitable catalysts for producing; the present polymers arethe known oxygen-liberating organic orinorganic peroxides such as benzoyl peroxides, di-tertiary butyl peroxide; tertiary butyl hydroperoxide, potassium persulfate, etc. Acidsalts. of. the. Friedel-Crafts type such as anhydrous aluminum chloride, or boron trifiuoride may also be employed.

. When polymerization. is carried" out in mass,.; the polymer is obtained. directly asatransparenh? glassy resin, of varying degrees'of hardness which maybe ground, and which product is soluble in mineral lubricating oiis. Thmrate of solution of the; polymer in oils. may be hastened by heating the. oils, and. by employing. vigorous. agitation. Usually trom 0.1% to 12% by weight oipolymen' will be found. sufficient for most lubricating pur-. poses. Any isomer of cyclohexylstyrene, that.

2 either ortho-, metaor para-cyclohexylstyrene may be employed.

When polymerization is carried out in: solution the monomeric cyclohexylstyr-ene is dissolved in a solvent therefor, which solvent may be toluene,

Xylene, cyc-lohexa-ne, etc., the solution so formedbeing heated until a test shows that the monomeric material has been. substantially completely converted to the polymeric body. The solution may then be concentrated! by the evaporation of thesoljvent in. order to produce a more concentrated solution. which solution may then be added directly to amineral oil to produce our improved lubricating composition. In some cases the polymerization may be carried out directly in a minerakoil, polymerizationbeing carried out at the desired temperature. either with. or without. a catalyst until the polymeric material has been formed in the mineral oilsolution- The mineral oil solution so formed may be used directly as-a lubricating composition; however, it is generally more desirableto. prepare such. a composition of. a concentration. somewhatin excess of that which is finally desired and then to dilute the solution after polymerization. oithe cyclohexylstyrene to the point where the desired ultimate concentration has been obtained.

In some cases, where it is desired to-obtain-the polymeric cyclbhexyl'styrene in substantially pure. form, the solution formed polymer is precipitated fromthe solution in which it has been producedby pouring the solvent containing the polymer into a non-solvent for the polymer. Suitable non-solvents. for. polymeric cyclohexylstyrene. are the. lower alcoholssuchas methyl, ethyl or; propyl. alcohol. Upon combining hydrocarbonw solutions. of? the polymer with any of the above. alcohols... the. polymer is precipitated and may be recoveredby filtration, washed free ofv solvent and. precipitant and then dried by exposure. to heatediair. The, polymeric. material so obtained. is a finely divided; white powder which is readily soluble in mineral" lubricating oils.

Emulsion. polymerization of" cyclohexyl'styrene. may be carried out by emulsifying, the monomeric material in water either with or. without an. emul'rsifying agent, but with intensive agitation. The emulsion s0 iormediis; heated for a periodoftime necessary toyieldia substantially completely polymerized product. Residual monomeric materiall Example 1 100 g. of para-cyclohexylstyrene was heated in a glass flask at 125 C. for one week. The hard, resinous polymerized para-cyclohexylstyrene was removed from the flask, reduced to a small particle size and then sufficient of the polymeric product was added to xylene to give a 2% by weight solution. The viscosity of this xylene solution was measured and found to be 1.32 centipoises at C. The apparent average I molecular weight of this'jsample, as determined by the elevation of the boiling point of a solution in toluene, was 17,500.

A'3% by weight solution of this same polymeric product was made in two types of oil, viz: a light hydraulic base oil and a heavy lubricating oil, the oils employed having the following properties:

Hydraulic Oil Lubricating Oil, Not Before After Heated Heating Heating Vis. at 100 F cS 3. 55 4. 12 119. 2 Vl'S. at 210 F .cs 1.32 1.44 12.02 Vis. Index 98 89 98 Slope 0.83 0.82 0. 87

-The viscosity properties of the 3% solution prepared as above was determined and found to be as follows:

Hydraulic Oil Lubricating Oil, Not Before After Heated Heating Heating VisIat 100 F. 7. 95 13. 47 154. 4 Vis. at 210 F 5. 53 4.16 32. 79 ViS. Index. 258 222 145 Slope 0. 17 0. 56 0. 38

Example 2 100 g. of monomeric para-cyclohexylstyrene was dissolved in 500 cc. of ethyl chloride. 0.1% of aluminum chloride (based on weight of paracyclohexylstyrene) was added, the addition being made after the cyclohexylstyrene had been cooled to a temperature below 10 C. but above 40" C. The solution so formed was maintained at this temperature for about minutes, after which the product was poured into alcohol, thus precipitating the polymer which was then recovered by filtration and drying. The average molecular weight, as determined by boiling point elevation in toluene, was 15,000.

A 3% solution of a polymer was made in the hydraulic oil employed in Example 1 above, giving a solution of polymer in oil having the following characteristics:

Hydraulic Oil Lubricating Oil, Not Before After Heated Heating Heating Example 3 g. of para-cyclohexyl'styrene containing 3% of benzoyl peroxide was heated first at 70 C. for one day, then at 100 C. for two days, and then at C. for two days. The hard, polymeric material was then dissolved in the hydraulic oil described in Example 1 above, and viscosity measurements made on the solution so formed. The following values were obtained:

Hydraulic 011 Before After Heating Heating Vis: at 100 F 5.00 5. 39 Vis. at 210 F 1. 77 1. 86 Vis. Index 137 134 Example 4 100 g. of para-cyclohexylstyrene was heated at a temperature of 125 C. for five days. The polymeric material so obtained had a molecular weight of 2400 asdetermined by the elevation of the boiling point of toluene. This material was added to samples of hydraulic and of lubricating oils as described in Example 1 above, and viscosity data obtained upon the solution. The data obtained in this manner were as follows:

Hydraulic Oil Lubricating Oil Before After Before After Heating Heating Heating Heating Example 5 Hydraulic Lubricating Oil Oil Vis. at 100 F cs.. 5.29 Vis. at 210 F ..cs.. 1.84 Vis. Index 104 ope 0. 75 0. 67

Example 6 100 g. of para-cyclohexylstyrene containing 1% by weight of benzoyl peroxide was heated at 70 C. for two days. The average molecular weight as determined by the depression of the freezing point in cyclohexane was about 9000.

Hydraulic Lubricating Oil Oil ViS. at 100 F cs 11. 10 295. 3 ViS. at 210 F--- -05-- 3. 83 27. 92 Via. Index... 237 120 Slope 0. 55 0. 59

An important property of the polymeric material resides in its ability to withstand the action of heat when dissolved in oil. In order to evaluate this property the light oil solution of the polymer was heated for '72 hours at a temperature between 120 F. and 125 F. At the end of this heating period the viscosity was again measured.

In the case of the lubricating oil, the oil solution was heated for a period of '72 hours at 342 F., after which heating period the viscosity properties were again measured.

The viscosity index, abbreviated Vis. Index in the above table, is obtained by calculation as described in Method D567-41, published in the ASTM Book of Standards, Part III, 1944, page 273.

While the concept of viscosity index has, in part, been widely used as a measure of the viscosity-temperature relationship of a mineral lubricating oil, more recently it is being realized that this concept is not completely descriptive. In view of this changed concept of the viscosity index values for lubricating oils, it is sometimes helpful to use, in addition to the viscosity index, a simple expression defining the temperature-viscosity relationship as the slope of a plot of the temperature-viscosity relationship on semi-log graph paper. The method of plotting the temperature-viscosity relationship is described in ASTM Specification D341-44. It will be realized by those skilled in the art that as far as the slope of the viscosity-temperature curve is concerned the desirable slope is one having as low a numerical value as is possible.

In the present specification, since both the viscosity index and the slope value are still in widespread use, examples of both values for certain compositions are given.

Example 7 0.5% by weight of poly-paracyclohexylstyrene was dissolved in an SAE 10 motor oil and the oil introduced into the crank case of a Lauson test engine. The test was conducted for a total of 36 hours. Samples of oil were removed at the end of 12, 24 and 36 hours and tested for viscosity and neutralization number.

The test results follow:

Oil before test:

Viscosity 210 F. SUS 45.98 Viscosity 100 F. SUS 162.1 Viscosity index 127.7 Neut. No. Nil

After 12 hrs. operation:

Viscosity 210 F. SUS 45.60 Viscosity F. SUS 158.9 Viscosity index 127.7 Neut. No. Nil After 24 hrs. operation:

Viscosity 210 F. SUS 45.82 Viscosity 100 F. SUS 162.6 Viscosity index 126.4 Neut. No. 0.05 After 36 hrs. operation:

Viscosity 210 F. SUS 45.98 Viscosity 100 F. SUS 163.2 Viscosity index 127.7 Neut. No. 0.1

The present compositions, while being suitable for general lubricating purposes, may also be used for any purpose for which a liquid composition having an improved temperature-viscosity relationship is edsired. Accordingly, the hereindescribed compositions are useful in hydraulic mechanisms of various types such as brakes, hydraulic transmissions, pumps and recoil mechanisms, lubrication of gears and turbines, etc.

In view of the stability of the herein-described composition against oxidation and the action of acids, these materials are particularly valuable for general automobile engine lubrication purposes.

What we claim is:

1. A mineral oil having lubricating properties containing an oil-soluble polymerization product of ar-cyclohexylstyrene in amount suificient to increase the viscosity of said oil.

2. A mineral oil having lubricating properties containing from 0.1% to 12% by weight of polymerized ar-cyclohexylstyrene.

3. A mineral oil having lubricating properties containing as a material for increasing its viscosity a small amount of an oil-soluble polymerization product of para-cyclohexylstyrene.

4. A mineral oil containing a naturally occurring wax in amount sufficient to crystallize upon cooling and in addition a small amount of an oil-soluble polymerization product of ar-cyclohexylstyrene in amount suflicient to inhibit the crystallization of said wax.

RAYMOND B. SEYMOUR. FREDERIC L. MATTHEWS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,998,350 Wuefi Apr. 16, 1935 2,072,120 Mikeska Mar. 2, 1937 OTHER REFERENCES The preparation and polymerization of some alkyl styrenes, by Marvel et al., in the Journal of American Chemical Society, vol. 68, pages 1089 and 1090. 

